HIF-2α enhances neutrophil recruitment to the synovium in a mouse model of acute inflammatory arthritis. (A) Schematic representation of K/BxN serum-induced inflammatory arthritis. The inflammatory response was measured as paw thickness (mm) in cKO P2 mice (B) and in cKO P2H2 mice (C) vs their representative control littermates (n = 4). Data are representative of ≥6 (B) and 3 (C) individual experiments. Neutrophil recruitment was assessed via flow cytometry analysis, measured as absolute numbers (Abs. cell n^o) of neutrophils and macrophages in the synovial cavity in cKO P2 mice (n = 5-8) (D) and cKO P2H2 mice (F) vs WT littermates (n = 9-12). (E) Representative images of Gr1 immunofluorescence staining of the synovial cavity (dashed line) 5 days after the start of the experiment (scale bars, 50 μm). Data are represented as mean ± standard error of the mean. *P < .05, Mann-Whitney U test.